The project proposed is intended to elucidate the mechanisms by which the dominant follicle (DF) and corpus luteum (CL) participate in the regulation of foliculogenesis during the primate ovarian cycle using cynomolgus monkeys as a non-human primate model. These studies are a direct continuation of my earlier work and are designed to determine by what mechanism the DF inhibits the development of competing follicles to restrict the ovulatory quota to unity. First, I will test the hypothesis that the DF inhibits the growth of other, competing follicles by secreting a substance that acts directly on the ovaries. I will also test the hypothesis that the CL inhibits follicle growth on both ovaries by a direct intraovarian action of progesterone. I will examine the proposed role of FSH in regulating the size of the ovulatory quota and determine the importance of a potential relationship between "inhibin" secretion by the DF and FSH secretion. I will test the hypothesis that high levels of estrogen in the DF's "microenvironment" provide it the advantage to survive in a milieu otherwise unfavorable to follicle growth. I will continue studies on computer-assisted sterological analysis of the monkey ovary. I will attempt to estimate when the DF is recruited and also cohort size as a function of day-in-cycle. Both In Vivo and In Vitro approaches will be employed to accomplish these aims, including the use of rat pituitary and granulosa cell culture as bioassays and monkeys with hypothalamic lesions as a "hypophysiotropic clamp" model in addition to autoradiography, radioimmunoassay, and other techniques. Thus, these studies are intended to contribute to a better understanding of the primate ovarian cycle, in general, and of ovulatory follicle growth, in particular. Understanding the physiological regulation of folliculogenesis in this primate will be important in serving as a rational basis for the design of clinical program of fertility enhancement and programs of population control.